Studies will be made of the nature of the protein that is tightly bound to the ribosome and that influences the translation of specific messenger RNA's. Recently, it has been found that glycerol gradients can be used to separate a tightly bound protein from E. coli ribosomes. The resulting ribosomes have an altered translational specificity similar to what was previously found with T4 ribosomes and NEM-treated ribosomes. Preliminary tests indicate that the translational specificity of the glycerol-washed ribosomes can be restored to normal by supplementation with material found at the top of the gradient. Since the glycerol-washing procedure seems to result in fewer side effects than either T4 infection or NEM-treatment, this method of inducing translational changes will be studied in some detail. We will focus on the purification of the protein released from the ribosomes by glycerol treatment with the aim of identifying it as a known factor, i.e., ribosomal protein S-1 or IF-3 alpha, or as a new factor free of other activities that might produce a similar effect.